1. Field of the Invention
The present invention relates to a biopsy instrument, and to methods and apparatus for collecting tissue samples or the like from humans or animals, in particular by excising a segment from a tissue, using the biopsy instrument. The invention also relates to a loading assembly for a biopsy instrument and an impact damping element for biopsy instruments.
2. Description of the Related Art
The invention departs from an apparatus for collecting tissue samples by excising a segment from tissue, and a corresponding method for harvesting of tissue samples described in U.S. Pat. No. 5,655,542 (Weilandt), the entire disclosure of which is incorporated by reference into this specification.
In this specification, the terms "proximal" and "distal" are used with respect to the person extracting a biopsy sample. Thus, the proximal end of a biopsy apparatus is its rear end, proximate the practitioner, and pointing away from the patient.
The biopsy instrument of the '542 patent includes a first part having an end with means for penetrating a tissue at the end, and a wall having an opening extending through the wall of the first part; and a second part adapted for being slidingly disposed on the first part, excision means for separating a segment of the tissue then penetrated by the first part provided on the second part such that sliding movement of the second part on the first part in one direction causes the excision means to pass through the opening in the wall of the first part thereby separating a segment of the tissue for extraction.
The method of harvesting biopsy samples of the '542 patent includes the steps of injecting the biopsy instrument into tissue to a position proximal of a sample to be taken; displacing simultaneously the first part and the second part of the biopsy instrument for reception of the sample in the first part; displacing the second part to sever the sample from the tissue.
The first part may take the form of a canula and the second part that of a tube in which the canula is slidingly arranged. The tube is provided with a finger at its distal end, the finger entering an opening in the canula wall in the tissue-severing step when the tube is displaced in a distal direction with respect to the canula.
The joint displacement of the first part and the second part following the injection step is accomplished by spring means, in particular a steel coil. Compression steel coils have been found to work well in practice, except for very powerful springs providing high acceleration to the combination of the first and the second part. High acceleration is attractive since, thereby, the use of separate driving force for the second step becomes superfluous, the displacement of the second part with respect to the first part being accomplished through the inertia of the second part. Moreover, high acceleration allows for less variation in sample quality when using the instrument with a variety of tissues. The loading of a biopsy instrument provided with powerful spring means which have to be compressed in the loading procedure constitutes another problem.